1. Field of the Invention
The present invention relates to a circuit breaker for breaking an electric circuit for a short time.
2. Description of the Related Art
In an electrical equipment system provided in a vehicle, when a certain abnormality is generated in a load such as a power window or the like or a certain abnormality is generated in a wire harness or the like constituted by a plurality of electric wires for connecting a battery to respective loads, a great current fuse interposed between the battery and the wire harness is melted and broken so as to break a communication between the battery and the wire harness, thereby preventing the respective loads, the wire harness or the like from being burned out.
However, in the electric equipment system using the great current fuse mentioned above, since the great current fuse is melted out and broken only when a current equal to or more than a predetermined allowable value flows through the great current fuse, even in the case that a certain abnormality is generated in the load such as the power window or the like or a certain abnormality is generated in the wire harness or the like for connecting the battery to the respective loads, there is a case that the circuit can not be broken and the various loads, the wire harness or the like can not be protected.
The present invention has been made by taking the matters mentioned above into consideration. Accordingly, an object of the present invention is to provide a circuit breaker which can protect electric parts by securely breaking a circuit for a short time.
Another object of the present invention is to provide a circuit breaker which can securely break a circuit for a short time even in the case that an abnormality signal is not sent due to a trouble of a control portion or the like.
In order to achieve the objects mentioned above, according to a first aspect of the present invention, there is provided a circuit breaker comprising: a heating portion charged with heating agent and having a conductivity, the heating portion being arranged between a first connecting terminal connected to a power source side and a second connecting terminal connected to a load side, and the heating portion being brought into contact with each of the first connecting terminal and the second connecting terminal; an ignition portion for causing the heating agent charged in the heating portion to generate heat by igniting an ignition agent; an expandable/contractable elastic member arranged near the heating portion or in contact with the heating portion and pressing the heating portion; an outer container receiving the elastic member, the ignition portion and the heating portion; a pressing operation restricting member preventing the elastic member from being pressed to the heating portion, the pressing operation restricting member being melted due to heat of the heating agent; and a heat conduction member bringing any one of the first connecting terminal and the second connecting terminal into contact with the ignition portion, wherein the circuit breaker normally supplies a current from the power source to the load, and the circuit breaker breaks a circuit from the power source to the load when the vehicle is abnormal.
In accordance with the invention mentioned above, when an excessive current flows through the first connecting terminal and the second connecting terminal, a temperature of the connecting terminals is increased due to the excessive current, a heat in one connecting terminal is conducted to the ignition portion via the heat conduction member and the ignition portion is ignited due to the heat. Then, the heating agent charged in the heating portion generates heat, the pressing operation restricting member is melted due to the heat and the elastic member is expanded so as to jump up the heating portion, whereby the electric connection between the heating portion, and the first connecting terminal and the second connecting terminal is broken, so that it is possible to securely break the circuit for a short time.
In accordance with a second aspect of the present invention, as it depends from the first aspect, the ignition portion ignites the ignition agent on the basis of an abnormality signal input from a control portion provided in an outer portion at a time of the abnormality of the vehicle so that the heating agent generates heat.
In accordance with the invention mentioned above, since the ignition portion ignites the ignition agent on the basis of the abnormality signal input from the control portion provided in the outer portion at a time of the abnormality of the vehicle such that the heating agent generates heat, it is possible to securely break the circuit for a short time also by an input of the abnormality signal. Further, even in the case that the circuit can not be broken since the abnormality signal is not input to the ignition portion due to the trouble in the control portion or the like, it is possible to securely break the circuit for a short time due to the temperature of one connecting terminal and it is possible to protect the electric parts.
In accordance with a third aspect of the present invention, as it depends from the first or the second aspect, the ignition portion has a pair of ignition portion terminals, a resistance provided between the pair of ignition portion terminals and the ignition agent arranged near or in contact with the resistance; one of the pair of ignition portion terminals is brought into contact with one end of the heat conduction member; another ignition portion terminal is connected to the control portion; and another end of the heat conduction member is brought into contact with the one connecting terminal.
In accordance with the invention mentioned above, since the temperature of the first connecting terminal is increased due to the excessive current and the heat due to the temperature increase is conducted to the first connecting terminal, the heat conduction member, one ignition portion terminal, the resistance and the ignition agent, it is possible to ignite the ignition agent due to the heat. Further, since another ignition portion terminal is connected to the control portion, the abnormality signal from the control portion is sent to the resistance via another ignition portion terminal and the ignition agent can be ignited due to the heat generation of the resistance.
In accordance with a fourth aspect of the present invention, as it depends from one aspect among the first aspect to the third aspect, the control portion has an electromagnetic coil through which an exciting current flows on the basis of the abnormality signal; and the control portion further has a switch having one end connected to the another ignition portion terminal and another end which is grounded, thereby the switch is turned on due to the exciting current.
In accordance with the invention mentioned above, in the control portion, when the exciting current flows through the electromagnetic coil on the basis of the abnormality signal, the switch is turned on due to the exciting current. Accordingly, the current flows from the power source along a path of the first connecting terminal, the heat conduction member, one ignition portion terminal, the resistance, another ignition portion terminal, the switch and the earth, so that it is possible to ignite the ignition agent due to the heat generation of the resistance and it is possible to break the circuit by using the power source provided in the connecting terminal side.
In accordance with a fifth aspect of the present invention, as it depends from one aspect among the first aspect to the fourth aspect, the pressing operation restricting member mounts the elastic member in a compression state and is freely attached to and detached from the outer container; the pressing operation restricting member is arranged near or in contact with the heating portion when being mounted to the outer container; and the pressing operation restricting member is an attaching and detaching member which is melted due to heat of the heating agent.
In accordance with the invention mentioned above, the attaching and detaching member mounting the expandable/contractable elastic member in a compression state is arranged near or in contact with the heating portion when being mounted to the outer container. When the ignition portion is ignited, the heating agent charged in the heating portion generates heat, and the attaching and detaching member is melted due to the heat. Since the elastic member is expanded so as to jump up the heating portion, it is possible to securely break the circuit for a short time so as to protect the electric parts. Further, since the attaching and detaching member is structured such as to be freely attached to and detached from the outer container, it becomes easy to attach and detach the attaching and detaching member. Further, since the elastic member is held by the attaching and detaching member, no external force is applied to the connection portion between the first connecting terminal and the second connecting terminal, and the heating portion.
In accordance with a sixth aspect of the present invention, as it depends from one aspect among the first aspect to the fifth aspect, a side wall portion is formed in an end portion of the heating portion; and respective front end portions of the first connecting terminal and the second connecting terminal are bonded to the side wall portion by a material having a low melting point.
In accordance with the invention mentioned above, since the respective front end portions of the first connecting terminal and the second connecting terminal are bonded to the side wall portion by the material having a low melting point, the heating portion is jumped up when the pressing operation restricting member and the member having a low melting point are melted due to the heat generation of the heating agent, whereby an electric connection between the first connecting terminal and the second connecting terminal is broken. Accordingly, it is possible to securely break the circuit for a short time so as to protect the electric parts. Further, since no spring force is applied to the material having a low melting point corresponding to the connecting portion between the first connecting terminal and the second connecting terminal, and the heating portion, it is possible to improve a reliability of the connecting portion.